[unreadable] This proposal requests funds for a Thermoelectron (Sunnyvale, CA) model LTQ FT22000 hybrid linear ion trap/Fourier transform mass spectrometer, equipped with an electrospray ionization (ESI) source, infrared multiphoton dissociation (IRMPD) and electron capture dissociation (ECD). The instrument would directly benefit a group of major users all of whom have NIH research support and all of whom currently use mass spectrometry in their research. Many of the investigators are participants in one or more NIH-supported roadmap and program project grants, which incorporate mass spectrometric analysis as an integral part of the research effort and provide a means for expanding the number of investigators benefiting from these resources. This includes the Johns Hopkins Center for Proteomics of Ischemia and Hypoxia (N01 HV28180, supported by NHLBI) and the Johns Hopkins Technology Center for Networks and Pathways of Lysine Modifications (TCNP U54 RR020839, supported by NIH). All of the features and capabilities of this instrument, which distinguish it from those available on current instruments at Johns Hopkins, will be utilized. In work by several investigators on lysine modifications and the structures of histones, high mass resolution (50,000 to 100,000) will distinguish trimethyl and acetylation sites (which may exist at the same site on different molecules). ECD and IRMPD will be used to fragment the very large branched peptide structures resulting from SUMOylation, as well as very large, partially digested peptide fragments needed to map polyacetylated lysines in histones and histone transferases. ECD will also be critical for the structural analysis of carbohydrates, O-linked glycopeptides and negatively charged post- translational modifications, primarily phosphorylation. Many of the studies here are proteomics studies, utilizing protein databases for identification of proteins in complex mixtures (as well as their PTMs) from their digested peptides. High mass accuracy (1-5 ppm) is key to providing correct identifications. The instrument will be housed in and managed by the Middle Atlantic Mass Spectrometry Laboratory and operated by four individuals representing the Major Users and collaborators. [unreadable] [unreadable] [unreadable]